The final phase of ending the United States' "forever war" in Afghanistan formally began Saturday after 20 years as the last U.S. and NATO troops are expected to withdraw by the end of summer.
U.S. President Joe Biden had set May 1 as the official start of the withdrawal of the remaining forces -- about 2,500-3,500 U.S. troops and about 7,000 NATO soldiers.
The U.S. is estimated to have spent more than $2 trillion in Afghanistan in the past two decades, according to the Costs of War project at Brown University, which documents the hidden costs of the U.S. military engagement.

